That's a fair point. When I wrote "centralization" I mainly meant components rather than development model. Systemd is very "centralized" in that a single package does a lot, but Linux as a whole is very decentralized in development model. BSDs are "centralized" in the sense that they have a single tree in source control, but the main result is a rather small, very configurable base system. (Then you deal with ports and packages on top, which feels more like a Linux distro: scripts that pull distfiles from lots of different sites and apply patches; not unlike the experience of building a .deb from source.)